import math

def num(x,y):
    return (x-y*math.sqrt(3))/2

r = 2
h = r - r*math.cos(30)
a = math.pi*r/3
l = a + (h*h)/r

print(f'a={num(11,3):.4f},b={num(11,4):.4f},c={num(9,3):.4f},d={num(9,4):.4f}')
print(f'会圆法计算弧长为{l:.4f}')
